According to an improvement in performance of a semiconductor device, a technique for having wirings with higher density and higher integration is required for a process of manufacturing a semiconductor device. For such process of manufacturing a semiconductor device, CMP (Chemical Mechanical Polishing) is an essential process now. In accordance with a progress in micronization of a semiconductor circuit, higher flatness is required for irregularities on a pattern wafer, and thus it is needed to achieve high flatness of nano-order by CMP. To achieve even higher flatness by CMP, it is preferable that the convex part of a pattern wafer is polished at a high polishing rate while the concave part is not much polished.
Herein, when a pattern wafer consisting of a silicon nitride film (SiN film) is used, the silicon nitride film generally has irregularities, and thus not only the convex part but also the concave part is scraped off at the time of polishing such material. Accordingly, it is difficult to sufficiently remove the irregularities.
Furthermore, a semiconductor wafer is composed of different materials like polycrystalline silicon for forming a circuit, a silicon oxide as an insulating material, or silicon nitride for protecting a surface of silicon dioxide which is not a part of a trench or a via against damages during etching. For such reasons, a phenomenon like dishing, in which a material like polycrystalline silicon or silicon oxide that is relatively soft and can easily react with a polishing agent is excessively scraped off compared to neighboring silicon nitride or the like, occurs and thus differences in the height are remained.
From the above, it is required to remove sufficiently the differences in the height during a step for polishing a pattern wafer which consists of a hard and chemically stable material like silicon nitride.
As a technique for responding to the above requirements, in JP 2009-530811 W (US 2007/209287 A), a chemical mechanical polishing composition with pH of from 1 to 6 which is for use in polishing simultaneously a circuit material containing tungsten and titan nitride as a hard coat layer and contains (a) a polishing agent, (b) 0.1 mM to 10 mM of malonic acid, (c) 0.1 mM to 100 mM of aminocarboxylic acid, (d) 0.1 mM to 100 mM of sulfate ion, and (e) water is disclosed.
Furthermore, in JP 2012-040671 A (US 2013/146804 A), as a polishing composition allowing polishing of a polishing object with insufficient chemical reactivity such as silicon nitride at higher speed compared to polycrystalline silicon or the like, a polishing composition containing colloidal silica which is immobilized with organic acid and having a pH of 6 or less is disclosed.